Method of improving the surface of copper and copper alloy castings



retented se 21,1938

j U IT D ls-mes.

" METHOD or mnovmo 'rns SURFACE oorrnn ann'ooeeannnnr casrmos Cyril Stanley Smith, Cheshire, Conm, manila i @Z Anaconda Copper Mining. Company, Newlorh'g '1.) Q N. Y., a commtlonof Montana No Drawing.

Application October 10, 1937,

Serial No. 169,462

4 Claims. (01. 22-214) I 1 long years of trial and errorca-s'ters have arrived and almost always some form of solid carbon which-will give good results with a particular alloy, but in many-cases it is still very difllcult to obtain a casting with a really good surface. The

bottom of the casting or other places where the stream of metal strikes against the mold is particularly apt to be bad, for the splashed drops of metal will frequently not melt into the main bodyand will remain, causing surface defects.

99 I have found that the introduction of a small amount of a volatile flux, such for example as ammonium chloride, into the bottom of a mold previously dressed in the usual way will considerably improve the surface of the bars and espe- 25 cially will benefit the extreme lowest partof the,

casting which is most liable to have surface defects if cast without any addition. e As a particular example of the application 0 my invention '1 have found that in casting a 350 pound bar of oxygen-free copper in a vertical copper mold dressed with a mixture of mold 011 and graphite with or without an addition of bone;

black, the surface can be greatly improved by the introduction of about ten grams of powdered ammonium chloride in the bottom of the'mold in such a location. that the stream of metal on reaching the? bottom strikes the ammonium chloride and so vaporiz'es it. This copper was melted in the presence of charcoal in a direct arc electric I 40 furnace and poured out of contact with air at a temperature of about 2150 F. at a rate of about 350 pounds. per ninute,but as described later Iv invention, produces a good, surface on bars that have been pourediat a 'slow enough rate to be sound. The ammonum chloride canbedroppedin from the top-ofthe mold, or it may beiplacedon the bottom plate before closing the moldfo'r it at certain compositions, usually containing an oilof ammonium chloride may vary from only afraction of a gram up to several hundred grams depending on the size and particular conditions of casting and will vary with the type and shape of mold, and the temperature and rate at which 5 the'molten metal is poured, the height through which it falls and many other factor The ammonium chloride should, however, alway'sbe at least partly vaporized or dissociated by contact with. the hot metaL- a j 110 another way ofintroducing the ammonium chloride into the mold is by adding it'to the; dressing itseIL-and. this can be done by mixing it asa dry powder in an oily dressing, or as an aqueous solution in those types of dressing'con Q. 1 J

sisting ofa suspension of boneasnbone black, v p and/ or carbonaceous material in water, the dress ing being allowed to'dr'y on the surface of the mold. -However, my experience shows it is preferable to place the dry ammonium chloride in-the 2 bottom of a previouslydressed mold as above de-" When pouringjdeoiddized copper into oil dressed i f molds water is sometimes allowed to run in at'the same time as the copper -,for. the purpose of improving the surface. '1 have found thattheuse of an aqueous solution of ammonium chloridein. place of water still furtherimproves the-surface; Additional ammonium chloride may alsoibe placed i the bottom of, the mold beforecasting f is commenced'either dry orin' concentrated solution and will be effective when either wate'r or ammonium "chloride solution is introduced with thecopper..-

1 I I Additions of 'anunonium'chloride in the mold may 7 be' advantageously employed not only in casting deoxidized or oxygen-free copper but also I 'in the castingof'copper alloys such as, for example, the bra'sse's, bronzes, the silicon bronzes, copper nickel alloys and alloys of copper-with l0 aluminum or with cadmium. In each case the amountnecessary, and the exact method of application [will vary, depending on casting condi-- tions as outlined above. Ammonium chloride may also be used in sand molds 'forymaking castings of deoxidized copper or copper alloys. I have'found that the addition of ammonium chloride is generally less effective in the'fcasting of these copper alloys than in making castings of oxygen freejor deoxidized copper.

'- I have also found that phosphorus pentoxide,

' .phosphori 'c' acid, and ammonium phosphatehave a similar effect when placed on the bottom of the mold and'thevolatilemetallic chloridesf'such as may be introduced in any other way. The amount, the chlorides of, iron, aluminumrzinc and ,cad- .85 I

mium are also effective. These substances have in common the property of volatility and the power of attacking metallic oxides which characterizes a flux. Although any 01' these volatile fluxes is eflective in improving the surface of ;-copper castings when introduced into the mold in substantially the same manner and amount as described above for ammonium chloride, in genera] I prefer to use ammonium chloride since it is effective, cheap, and is not 'deliquescent under ordinary atmospheric conditions.

Having thus set forth the nature of my invention, what I claim is:

1. The method of improving the surface of castings of'copper and its alloys-which comprises introducing a volatile flux into a dressed metallic mold and pouring the molten metal therein.

' mold cavity a quantity of ammonium chloride, [and pouring the molten metal or alloy into the mold.

cm sum? SMITH. 15 

